Meiosis II is the second division in the meiotic process, and it's very similar to a normal mitotic division. Here's a breakdown of the chromosome behavior:
1. Prophase II:
* The nuclear envelope breaks down again.
* The centrioles move to opposite poles of the cell.
* Crucially, NO DNA replication occurs in this phase. The chromosomes are already replicated from Meiosis I.
2. Metaphase II:
* The chromosomes, each consisting of two sister chromatids, line up along the cell's equator (metaphase plate).
* The sister chromatids are attached at the centromere and are facing opposite poles. This arrangement sets the stage for separation.
3. Anaphase II:
* The centromere of each chromosome splits, separating the sister chromatids.
* The newly separated chromatids, now considered individual chromosomes, are pulled towards opposite poles by spindle fibers.
4. Telophase II:
* The chromosomes reach the poles and decondense.
* The nuclear envelope reforms around each set of chromosomes, forming two new nuclei.
* Cytokinesis (the division of the cytoplasm) occurs simultaneously, creating four haploid daughter cells.
Key Differences from Meiosis I:
* No DNA replication: Chromosomes are already replicated from Meiosis I.
* Sister chromatid separation: Meiosis II separates sister chromatids, resulting in haploid daughter cells.
* Four daughter cells: Meiosis II produces four haploid daughter cells, each with half the number of chromosomes as the original parent cell.
In essence, Meiosis II ensures that each of the four daughter cells receives a single copy of each chromosome, contributing to the genetic diversity of gametes.
